The present invention is directly related to and is an improvement of the improved plug-in base assembly disclosed in U.S. Pat. No. 4,714,431, issued Dec. 22, 1987. The improved plug-in base assembly of U.S. Pat. No. 4,714,431 is directly associated with the electrical distribution systems disclosed in U.S. Pat. Nos. 4,673,229 issued Jun. 16, 1987 and 4,820,177 issued Apr. 11, 1989. Each of the previously referenced patents are assigned to the same assignee as the present invention and are incorporated by reference for the description of common features and applications.
It is common in the art of electrical distribution systems to include provisions for the installation of tap-off units at intervals along a busway housing. These provisions generally include a number of access openings spaced at set intervals along the busway housing whereby access to the bus bars enclosed therein is obtained. Each access opening includes a plug-in base made from an electrical insulating material. The plug-in base provides support for the bus bars and serves as a mounting platform for the tap-off unit. Each plug-in base includes a number of plug-in openings through which the electrical connection of a tap-off device is made. These openings are of sufficient size to permit unintentional contact of a human finger with the exposed edge of an uninsulated bus bar positioned immediately behind the plug-in base. A door is provided for covering the outside surface of the plug-in base including the plug-in openings when no tap-off unit is installed on the base. The door is open, both immediately before the installation and after the removal of a tap-off unit. With the door open there is an increased possibility of unintentional contact with the uninsulated edges of the bus bars through the plug-in openings in the plug-in base.